class_docstr: The following is a list of string that can be specified to ``use_up_to`` option in ``__call__`` method;
  
  * ``'detection'`` (default): The output from the last convolution (detection layer) after post-processing.
  * ``'convdetect'``: The output of last convolution without post-processing.
  * ``'lastconv'``: Network till the convolution layer+relu which comes before detection convolution layer.
  
  References:
      * `Joseph Redmon et al., YOLO9000: Better, Faster, Stronger.
        <https://arxiv.org/abs/1612.08242>`_
code: def _input_shape(self):
      return (3, 416, 416)
  
file_path: nnabla/python/src/nnabla/models/object_detection/yolov2.py
imports: from __future__ import absolute_import
  import nnabla
  from nnabla.utils.nnp_graph import NnpNetworkPass
  import numpy
  from .base import ObjectDetection
label_desc: Use image node_id 2 for calling the YoloV2 obj's underlying member method code with example usage: obj._input_shape() and returns: int,  int,  int